code: def test_HandleUnknownValue_HaveUnknownInTest_ExpectMean(self):
      train = pd.Series(["a", "a", "a", "b", "b", "b"], name="color")
      target = pd.Series([1.6, 0, 0, 1, 0, 1], name="target")
      test = pd.Series(["c", "b"], name="color")
      test_target = pd.Series([0, 0])
  
      enc = encoders.TargetEncoder(
          cols=["color"], handle_unknown="value"
      )
      enc.fit(train, target)
      obtained = enc.transform(test, test_target)
  
      self.assertEqual(0.6, list(obtained["color"])[0])
  
imports: import pandas
  from unittest import TestCase
  import tests.helpers
  import numpy
  from category_encoders.datasets import load_postcodes, load_compass
  import category_encoders
label_desc: Use image node_id 8 for calling the TestTargetEncoder obj's underlying member method code with example usage: obj.test_HandleUnknownValue_HaveUnknownInTest_ExpectMean() without return types